1. Field of the Invention
This invention relates in general to the field of textile manufacturing and in particular to a method of making textile articles possessing specific levels of durable antimicrobial activity in accordance with the requirements for particular applications.
2. Description of the Related Art
Textile articles composed of various fibers and/or polymers are used in many applications for which the possession of antibacterial activity would be desirable. For example, such articles and applications may include clothing, fabrics, and linens for use in hospitals, polymer-based materials for use in biomedical research, and woven cloth or metal fibers for use in sanitation or cleaning.
One method of imparting antimicrobial activity to textiles utilizes the addition of antibacterial chemical compounds, such as triclosan. However, one problem with treating textiles with antibacterial chemicals is that such compounds tend to wash out, wear out, or otherwise dissipate after relatively little use.
A means of impregnating a more durable antibacterial activity into textile articles has been accomplished through the addition of a substance known as zeolite. Zeolite is a volcanic rock predominantly made of aluminosilicate which is solvated by calcium and sodium cations. When zeolite is crushed into fine particles and added to a mixture of silver, copper, or zinc salts, the calcium and sodium cations in the aluminosilicate are replaced by silver, copper, or zinc metallic cations to form a compound known as "modified zeolite."
Experiments with modified zeolite demonstrated that the metallic cations, when ionized by the humidity in the surrounding ambient, produce intense electrical fields. These electrical fields lead to the release of oxygen, which has significant antibacterial effects. Furthermore, the metal cations of modified zeolite are capable of chemically mixing with bacterial cell walls, thereby causing growth disruption or destruction of bacterial cells.
It is known that these antibacterial properties can be customized to affect specific microorganisms. Depending on the chemical structure of their cell wall, particular types of bacteria can be disrupted or destroyed according to the metal salt used in the formation of modified zeolite. For example, copper or zinc cations act upon the cell wall of Gram-positive bacteria, whereas silver cations act upon the cell wall of Gram-negative bacteria.
U.S. Pat. No. 4,775,585 by Hagiwara et al. describes a polymer article containing zeolite particles in which a metal ion having bactericidal activity is incorporated in the zeolite by an ion exchange reaction. The polymer article is produced either by admixing metal-ion-containing zeolite particles with a polymer or by molding a zeolite-containing polymer into an article and then treating the article with a metal ion solution. The textile articles made by this method contain between 0.01% and 10% by weight zeolite particles that possess at least one metal ion in an amount less than 92% of the total ion exchange capacity of the zeolite.
However, the antibacterial fiber derived by the method described in the '585 patent has been difficult to exploit in the production of useful articles. Depending on the size and mix of the fibers used, the resulting fabrics have often been unpredictably ineffective or excessively active. For example, a mixture of an apparently adequate percentage of antibacterial fiber with an inert fiber might unexpectedly produce a low-efficacy fabric. Similarly, the resulting fabric might be so active as to destroy all forms of bacteria within its touch, which would render the product unacceptable for use in contact with human skin.
The method of Hagiwara et al. produces textile articles that have undefined levels of antibacterial activity; therefore, they must be tested to determine their level of antibacterial efficacy and the prior art does not provide any teaching for predicting it as a function of textile-design parameters. As will be described hereinafter, the present invention, among other advantages, provides a method of predicting antibacterial properties, thus eliminating the need for efficacy testing of the textile once the properties of the component fibers are known. Nothing has been taught in the prior art to predict the spatial effect of antibacterial fibers and to enable the design of fabrics with a predetermined antibacterial efficacy. The present invention is directed at providing such teachings.